Weird normals(I already Recalculate Normals,Remove doubles)
Ok, there are a couple of problems here.
The first and foremost is that you have many edges marked &quot;sharp&quot;.

To fix this, simply enter edit mode, select the whole mesh (A), right-click and select &quot;clear sharp&quot;

However, as you can see, the mesh is still affected because of &quot;ugly&quot; topology. Blender favors the use of Quad based topology, and though sometimes tri's or n-gons are unavoidable, they are best kept on flat (non curved) surfaces. To reduce the chance of shading based artifacts, always try to keep your mesh as quad-based as possible.

To fix this for your project, you can either re-topologize it manually, or an easier approach would be to use a Remesh Modifier, either in it's own, or in conjunction with manual adjustments.

Once this is done, if you want your mesh &quot;smooth&quot; again, you could add a Subdivision Surface Modifier, and shade smooth. (NOTE - the smooth shading did not work properly for me until I applied the Remesh Modifier. I am currently using 2.9, so I'm not sure if it's unique to this version, but if it isn't shading smooth for you, try applying the modifier first)